1. Field of Invention
This invention relates to cathodes for electrochemical drilling of holes having a substantial depth-to-diameter ratio, as much as 150 to 1, and more particularly to such a cathode having electrically insulating helical flutes on the exterior thereof to support the electrode in the hole being drilled and to provide an egress route for the electrolyte and remoted workpiece material. To make the cathode, flutes are formed by wrapping threadlike members helically around the exterior of the cathode tube and coating the tube and threadlike members so wound with an insulating layer to connect the helically wound thread members to the tube and form a helically fluted cathode of selected flute diameter.
2. Description of the Prior Art
The electrochemical drilling art includes cathodes of many different shapes including those taught in U.S. Pat. Nos. 3,708,404; 3,714,018; 3,285,844; 3,647,674 and 3,748,252 but none of these are helically fluted for the purpose taught herein. While Crawford et al U.S. Pat. No. 3,271,288 shows cathodes with a projection therefrom, it should be borne in mind that these are uninsulated projections used to form threads in the part being drilled as the cathode rotates in the workpiece hole.